This invention relates to electrical circuits extending between a tractor or truck and a towed unit or trailer of a highway semitrailer or truck-trailer combination, the internal circuits of an airplane on the ground, and the like. In particular, this invention provides a test connector which may be used for checking those electrical circuits.
For example, highway vehicles are required to have "running" lights and "taillights" for showing the presence of the vehicles to drivers and other vehicles which may approach or overtake the vehicles on a roadway during hours of darkness. Vehicles must have further lights for signaling, such that other drivers may know when brakes are being applied and when a left or right turn is intended. These lights operate from electrical circuits which extend from switches in the cab or driver's compartment to various locations on the sides and the rear of the vehicle. When a trailer is towed by another vehicle, the electrical circuits must pass through a flexible electrical cable which spans the towing vehicle and the trailer. In semitrailer combination vehicles, an electrical cable must extend between the tractor unit and the trailer unit of the combination vehicle. Electrical plug connectors are provided such that the cable may be conveniently disconnected when the vehicles are unhitched from each other, or when the tractor unit is separated from the trailer unit of a semitrailer combination vehicle.
In the interest of highway safety, the various electrical circuits of a truck-trailer combination vehicle must be frequently checked. Obviously, a simple check of the overall circuits would be to plug the connectors together and to test the circuits through the truck-trailer combination as a whole. A driver could operate the brakes, could turn on the various light switches, and could operate the turn signal control lever while another person standing behind and apart from the vehicle could observe the various lights. If a malfunctioning of one or more of the circuits is detected, a trouble shooter must determine the cause, and it then becomes important to establish whether the trouble is in the switches, wiring of the truck, or in the lamps or wiring of the trailer. Under these conditions, it has been found to be most expedient to unplug the connector to electrically separate the truck from the trailer such that the circuits of each unit can be separately checked. Indeed, it is frequently necessary to check the electrical circuits in one unit, such as the tractor or truck unit, without the presence of another companion unit.
It is an object of this invention to provide an improved means for checking electrical circuits common to a truck or tractor unit and a trailer unit of a semi-trailer combination vehicle. More particularly, it is an object of this invention to provide a pluggable test connector which will mate and plug into a connector of the vehicle unit for providing a visual indication of the functioning or malfunctioning of the electrical circuits.
It is a further object of this invention to provide an improved test connector for checking electrical circuits of a truck-trailer combination vehicle wherein said connector may be hooked onto and supported by a part of the vehicle. More specifically, it is an object of this invention to provide an electrically conductive hook arrangement for both supporting the test connector and for electrically grounding the test connector such that electric currents may pass through the indicator lamps which will provide visual indications of the functioning of the electrical circuits.